Fuselage segments of aircraft are conventionally fabricated via metal construction out of skin shells. The skin shells each consist of a sheet-like skin field, which is reinforced by a rear structure comprised of stiffening elements extending in a longitudinal and circumferential direction. The longitudinal reinforcements are attached to the metal body directly via riveting. The circumferential reinforcements are attached indirectly via riveted-on fittings.
However, more recent times have seen an increased use of fiber composites such as carbon fiber reinforced or glass fiber reinforced plastic components for manufacturing the fuselage segments. In one method of construction, the skin fields and stiffening elements along with the fittings are separately fabricated out of a resin-impregnated, web-like fiber plies, such as prepregs, and riveted after being subjected to final mechanical processing. The process of manufacturing a large-area skin field can be readily automated, thus making it cost-effective. However, the manufacture of stiffening elements and fittings pushes up the costs, since they need to be subsequently machined to the final dimensions, and then integrated into the skin field via riveting.
In light of the very high costs for riveting, in particular for riveting during use in carbon fiber-reinforced plastic compounds, a very high tolerance compensation, which can lead to assembly problems in particular given large component dimensions, as well as an expensive final machining of the stiffening elements and fittings, attempts are increasingly being made to design the fuselage segments integrally with a rear structure. In this so-called integral mode of construction, at least mostly the stiffening elements running in a longitudinal direction are integrally designed with the skin shell. This method is characterized by manufacturing in one shot, i.e., no subsequent riveting is necessary, at least with respect to the longitudinal reinforcements.
For example, DE 10 2008 029 518 A1 shows an infusion method. A thermoplastic binder is here used to position dimensionally stable fibrous semi-finished products on a dimensionally unstable, sheet-like fibrous semi-finished product that represents the skin field, and used as a support for dimensionally unstable fibrous semi-finished products. In a resin infusion process and an ensuing hardening process, the dimensionally unstable fibrous semi-finished products are bonded with the dimensionally stable fibrous semi-finished products to the skin shell with integrated rear structure. In a respective central region spaced apart in a vertical direction by a component head, the dimensionally stable semi-finished products acting as the mold cores each have an inner or integral resin supply channel extending in the longitudinal direction, which after the hardening process forms an integral component of the skin shell filled with resin residue. During infusion, the resin is upwardly pushed or guided from the resin supply channel in the direction of the component head, and downwardly in the opposite direction toward the sheet-like, foot-shaped fibrous semi-finished product. However, problems are posed by the positioning of the dimensionally unstable or dry fibrous semi-finished products on the mold cores, and the associated high technical outlay and reproducibly high component quality, for example with respect to a uniform resin distribution. In addition, the hardened resin residue arranged in the integral supply channels forms fiber-free component areas that reduce the component stability.